This invention relates to improvements in warehouse storage systems. In particular, it relates to improvements in storage systems designed to store large numbers of packages or cartons on racks or shelving by means of pallets.
Modern manufacturing techniques with large production runs, and other factors, have led to the requirement that stocks and inventory be stored in warehouses. The increasing technological sophistication and high quality of manufactured products has led to the need to store stocks and inventory in well built, clean, atmospherically controlled warehouses which are consequently more expensive. The demand for efficiency in modern manufacturing and marketing systems has led to the requirement that a wide variety of stocks and inventory be warehoused where they can be quickly and efficiently stored and retrieved as needed.
The result is that warehouses have become neat, efficient, well built and expensive. It is therefore important in the warehousing industry to make maximum use of these facilities by creating as much occupiable storage space as possible within a given warehouse or facility. In other words it is important to minimize the unoccupied storage space, such as access corridors and travelways for loading vehicles, etc.
The modern trend has been to provide racks on which shelves are provided to accept pallet-loaded containers or cartons and which are often three, four, and five levels high. These pallet supported cartons or containers are typically placed on shelves or retrieved from shelves by fork lift trucks or other transfer vehicles.
It is obvious that if every row of cartons requires a corridor in which a transfer vehicle can travel, the amount of warehouse space devoted to storage can never be more than approximately fifty percent of the available area. As a result racks with shelving have been developed which will accept three or four pallets located one behind the other so that one corridor will enable a transfer vehicle to access three or four times as much storage space. In order to employ this concept, it is necessary to provide means whereby pallet supported containers can be placed on a shelf and moved to the back a depth of two or three times the horizontal dimension of the pallet. These systems are commonly known as push back racks. Many of these systems use a series of rollers or wheels like loading ramps which will allow the pallets to be pushed to the far end of the lane or shelf and frequently they are inclined so that the pallets will flow by gravity to the front of the shelf as they are retrieved.
More modern systems have been developed which employ one or a series of carts which travel within the laneway of the shelf racks and are designed so that a pallet is placed on a cart and each subsequent pallet then pushes the previous pallet towards the back end of the shelf.
Since all of these carts must at some point travel to the front end of the shelf for loading, it is important that the carts be designed so that they can be all situated at the same location (i.e. at the front) on the shelf without obstructing or colliding with each other. Therefore, many of the systems designed to-date have achieved a degree of volumetric efficiency in the use of storage spaces in warehouses but in doing so have arrived at a rather complex and duplicated series of tracks to accommodate the wheels of two or more carts moving within the same shelf compartment or lane.
Furthermore, in order to permit two or more carts to occupy the same position on a shelf, they are structured so that the bed or platform of each cart is spaced above or below the next adjacent cart and this creates a certain loss of vertical dimension that results in a space occupied by the head room required for the carts.
It is therefore the purpose of this invention to provide a warehouse storage system of the push back type which can handle a row of three or four or more pallets on a single shelf. It is especially the purpose of this invention to provide such a system in which a series of two or three carts are provided to transfer pallets towards the end of the shelf safely and efficiently. It is also the purpose of this invention to provide a design for a push back storage system in which the carts are so designed that they will cooperate in a manner which occupies a minimum amount of vertical spacing between the bottom of the shelf and the top of the cart.
It is also the purpose of this invention to provide a push back system in which a series of carts may travel safely on tracks of a relatively simple, structurally strong, and inexpensive design.